The present invention relates in general to rotatable shaft combination lock mechanisms suitable for use in, for example, doors, safes, or portable padlocks. Typically, such rotatable shaft combination lock mechanisms include a plurality of gated tumbler wheels, but may also include other mechanisms which are actuated by rotation.
Conventional locks utilizing lock mechanisms of the general class known as combination locks typically include three or more tumbler wheels which are loosely journaled in coaxial longitudinally spaced relation for rotation on a spindle or drive shaft within the lock housing, where the drive shaft is accessed through the wall of the housing. Most typically, an indexed and finger manipulable wheel mechanism, or dial, is positioned on the outer surface of the housing. The wheel mechanism may be utilized to provide the required rotations of the drive shaft and tumbler wheels to unlatch the lock.
The external dial typically provides the operator with means to manually manipulate the internal drive shaft and tumbler wheels in accordance with a known code, or combination. The proper manipulation of the dial results in the unlatching and unlocking of the lock. In the three-tumbler-wheel system commonly used in the art, the operator generally rotates the external dial in a clockwise direction through angular positions to a first desired point, commonly referenced by a numeral, then rotates the external dial in a counterclockwise direction to a second desired point, commonly referenced by a numeral, and finally rotates the external dial again in a clockwise direction to a third desired point, again commonly referenced by a numeral. Following this typical procedure, the lock mechanism is unlatched and the lock may be opened.
Existing combination lock mechanisms are designed to be human friendly by including the discussed externally readable and finger manipulable dial. Notwithstanding the external indexing, the tolerances required for unlatching conventional locks are left quite loose, to further ease use by average persons. In a typical combination lock operable by a finger manipulable dial, the locking mechanism clearances are such that a slight over or under rotation of the dial will not be fatal to operation of the lock. Rather, clearances are designed to account for slight errors in precision.
For example, if a conventional combination lock has the combination 10-22-17, the lock is typically designed to be opened when a user rotates the dial clockwise three turns to the indexed numeral 10, counterclockwise two turns to the indexed numeral 22, and again clockwise one turn to the indexed numeral 17. However, it is conventional that tolerances are built in the lock mechanism such that rotations may be permitted to be off several digits, and the lock will still open. As an example, using the combination lock with the combination of 10-22-17, rotational input of 10-21-17 will likely open the lock. In fact, each of the rotations may be ceased or stopped at a digit which is “off” by more than only one digit, for example an input of 8-20-19 will likely still open the lock, even though each of the stopping points is “off” by two indexed positions.
There are several reasons for this built in sloppiness. These reasons most often have to do with human limitations regarding to dexterity, memory, and patience, which are all interrelated in some ways.
Regarding dexterity, even the most dexterous of humans are only capable of a certain level of positioning accuracy. In a typical peripherally gated combination lock, the lock manufacturers place a single gate at a location on the periphery of each wheel. This gate is sized to accept a side bar when the correct combination is entered. However, to account for the relative lack of dexterity exhibited by human manipulation, the gate is often much larger than the width of the side bar. If the gates were sized to include only a slight tolerance with the side bar, the rotational accuracy for opening a lock would be too tight for typical human manipulation. Of course, some humans may still be able to manipulate the lock for at least one indexed number accurately, but it would likely take a tremendous amount of time, effort, and concentration. That time, effort, and concentration weighs against the patience of the person. Thus, locks have heretofore been manufactured with gates which allow for a large tolerance with the side bar.
Also, the person's memory may fade over the time required to enter the rotational inputs required to unlatch the lock. For example, again using the combination above, if a person had to enter exactly 10-22-17, and no inaccuracies were tolerated, the person would have to spin the dial clockwise three times and stop precisely on the 10 position. The person would then have to rotate the dial counterclockwise two times and stop precisely on the 22 position. The concentration required to stop precisely on the second position may cause the person to forget the third digit of the combination, or forget the number or direction of rotations required for the final number of the combination. Other memory based complications may also interfere, such as external distinctions. Lock manufacturers thus build in a level of sloppiness that permits quick manipulation of the combination lock, for example by permitting the lock to unlatch even if a user is “off” by several digits.
Regarding memory, most conventional combination locks include three wheels, requiring the user to memorize a three-number combination. An example is the 10-22-17 combination discussed. If, however, the number of tumbler wheels were increased, the number of digits in the combination would be increased proportionally. Although this would permit more secure locks, the limits of human memory have contributed in discouraging the use of large numbers of disks.
Presently, among the most complicated of conventional locks are those used on bank vaults. Such locks may include four tumbler wheels, requiring a user to remember a four-number combination. Manipulation of such a lock taxes the abilities of users. The additional tumbler wheel not only requires the user to remember an additional number, but also increases the number of rotations required to open the lock. In the four-disk example, a user would have to first rotate the external dial four times in a clockwise direction, three times in a counter clockwise direction, two times in a clockwise direction, and finally one time in a counterclockwise direction, for a total of ten rotations. This is a lot of turns for a person to count while still remembering the combination and blocking outside interferences. Only in the most secure locations, bank vaults, is this tolerated. Most conventional locks are of the three-disk variety.
It is estimated that present commercial locks of the three-disk variety comprise 85% of the market while four-disk locks make up the remaining 15%. The greatest number of disks known to have been attempted in a commercial product is five, by Joseph L. Hall of Cincinnati, Ohio, in the mid-1800s. It is believed that this lock was only used for a short period of time due to the problems associated with manipulating five disks. No locks are presently known to embody five or more disks. Heretofore, the beneficial increase in security offered by a lock with greater than four disks has been severely outweighed by the difficulties associated with manipulating such a lock.
In addition to the added security provided by heretofore unheard of disk numbers, combination locks of the present invention also feature numerous other improvements, as will be discussed. One such improvement is the provision of much tighter tolerances within each tumbler wheel. Whereas conventional locks allow for a loose fit between the peripheral gate and the side bar, locks constructed in accordance with the present invention permit much tighter tolerances. Other of these improvements include the provision of a propriety (or non-propriety) female interface within the body of the cylinder lock which may only be engaged by a tool and is not finger manipulable. Accordingly, there may be no external dial. There may also be no visible demarcations on the lock housing associated with the combination.
The tool operated lock of the present invention therefore solves the inherent problems associated with limited human dexterity, memory, and patience by providing for a combination lock mechanism which may be manipulated and opened by a tool, or by a human in conjunction with particular tools. The functional arrangement of, and interrelationship between, the lock and the tool provides for security features, flexibility, and control not previously available from conventional locks. The tool operated combination lock of the present invention generally operates under the principles known in the combination lock art, with the additions of tighter clearances, greater numbers of disks (or tumbler wheels), and other improvements that could not have been realized in a practical sense until the novel mating of the combination lock with the speed and precision of the motorized tool. Tools for use with such locks are also disclosed herein.